Electrostatic recording device

ABSTRACT

An electrostatic recording device comprising a cathode-ray tube having a thin film window opposite its electron gun, an electrode spaced from the thin film window, an electrostatic recording sheet disposed adjacent the face of the electrode toward the thin film window, a DC power supply connected between the thin film and the electrode to supply a positive voltage to the latter, and means to multiply the number of electrons between the thin film and the recording sheet by ionizing a gas disposed therebetween.

United States Patent [72] Inventors YoshihiroUno Machida-shi; Hidehiko Kawakami, Kawasaki-shi, both of Japan [21 Appl. No. 763,518

[22] Filed Sept. 30, 1968 [45] Patented Oct. 5, 1971 [73] Assignee Matsushita Electric Industrial Co., Ltd.

Oaza Kadoma, Kadoma-shi, Osaka, Japan [32] Priority Oct. 3, 1967, Oct. 11, 1967, Oct. 12, 1967,

Oct. 13, 1967 [33] Japan [31 42/64193, 44/65873, 42/66220 and [54] ELECTROSTATIC RECORDING DEVICE 10 Claims, 9 Drawing Figs.

[52] 11.8. CI 346/74 ES, 13 1 [51] Int. Cl ..G0ld 1 5 /0 6 H0 1 j 33/04 [50] Field of Search 346/74 CR, 74 ES; 179/1002 CR; 340/173 CR; 178/66 TP; 313/74 [56] References Cited UNITED STATES PATENTS 2,777,745 1/1957 McNaney.. 2,839,602 6/1958 Fries 3,001,849 9/1961 Walkup....

3,341,856 9/1967 Bigelow.... 3,350,503 10/1967 Gregg 3,403,387 9/1968 Boblett Primary Examiner-Stanley M. Urynowicz, Jr. Assistant Examiner-Gary M. Hoffman Anorney-Stevens, Davis, Miller & Mosher 346/74 313/74 X 346/74 346/74 346/74 X 346/74 X ABSTRACT: An electrostatic recording device comprising a cathode-ray tube having a thin film window opposite its electron gun, an electrode spaced from the thin film window, an

electrostatic recording sheet disposed adjacent the face of the electrode toward the thin film window, a DC power supply connected between the thin film and the electrode to supply a positive voltage to the latter, and means to multiply the number of electrons between the thin film and the recording sheet by ionizing a gas disposed therebetween.

.PATENTEU 1101 51911 SHEET 3 OF 3 FIG. 6

INVENTORS II IHIRO luvo HIDE Hlno "mm/mu ATTORNEYS ELECTROSTATIC RECORDING DEVICE This invention relates to an electrostatic recording device employing a cathode-ray tube having a window in the form of a thin film which can be penetrated by an electron beam.

When electrons accelerated up to some .energy level impinge against a substance, the electrons penetrate to some depth which 5 dependent upon the energy possessed by the electrons and upon the properties of the specific substance. The electrons can pass through the substance if the substance is in the form of a thin film which is sufficiently thin compared with the penetrable depth of the electrons. Provided that this thin film has a sufficient strength, it is possible to employ the thin film as a vacuum-sealing window for a cathode-ray tube so that an electron beam emitted from an electron gun disposed within a high vacuum can be led out into the atmosphere through the window. The electron beam thus led out into the atmosphere from within the high vacuum through the thin film exercises a physical and chemical change on a medium to be acted upon by the electron beam, such as a photographic film, electrostatic recording sheet, polymer material or the like. A suitable means for applying a voltage may be disposed in an air space between the cathode-ray tube or electron-beam penetrative recording tube and a recording medium so as to multiply the number of electrons in the air space in which the voltage-applying means is disposed, thereby to effect a remarkable improvement in the sensitivity of recording.

It is therefore a primary object of the present invention to provide an electrostatic recording device employing a cathode-ray tube having an electron-beam penetrative window in the fonn of a thin film. The cathode-ray tube acts as a means for forming an electrostatic charge image variable depending on a signal so that the charge image can be formed on an electrical insulator by the electrons passed through the thin film or by ions produced by the electrons and can then be transfer-printed on a recording sheet so as to be made visible by a toner or ink.

The above and other objects, features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. l is a schematic sectional view of a recording tube having a window in the fonn of an electron-beam penetrative thin film employed in the device according to the present invention;

FIG. 2 is a schematic view illustrating the basic principle of the present invention;

FIG. 3 is a schematic sectional view of an embodiment of the present invention;

FIG. 4 is a graph showing the relation between all and El? where a is the first Townsend's coefficient, P is the gas pressure and E is the strength of electric field;

FIG. 5 is a graphic representation of the Paschen's curves for various gases;

FIG. 6 is a schematic sectional view of another embodiment of the present invention;

FIG. 7 is an enlarged sectional view of part of FIG. 6; and

FIGS. 8 and 9 are schematic sectional views of other embodiments of the present invention.

Referring to FIG. I, there is shown a recording tube having a window 1 of an electron-beam penetrative nature. The window l is a thin film ofa metal (Al, Ni, etc.), metal oxide such as alumina (AI,O,) or oxide of a semiconductor whose thickness lies within a range of a fraction of 1am. to several am. In case this film is an insulator or high-resistive material, it is desirable or needed to coat a side or both sides of the film with a suitable conductive material such as vacuum evaporated aluminum less than LOOOA. thick. An electron beam whose energy is in the order of several ten Kev. can easily pass through the thin film with such a thickness.

A thin film of a metal, metal oxide such as alumina (A1 or an oxide of a semiconductor is preferably employed as a partition in a device adapted for leading an electron beam from one atmosphere to another through the partition. The partition may be a single film having a required size or may have a unitary structure comprising such a film backed up by a suitable supporting member having a series of slits or perforations or a meshlike form.

Alumina is stronger than metals when it is compared with metals in terms of mass and its mechanical strength is far higher than that of aluminum proper. In addition to the above advantages, a metal oxide such as alumina is free from mechanical damage and does not tend to deteriorate since it is chemically stable. Therefore, such a metal oxide can favorably be used as an electron-beam transmissive window.

In FIG. 1, the window or thin film I is supported by a sup porting member 2 having 'a series of slits or perforations. The tube comprises an electron gun 3 for emitting an electron beam, a glass envelope 4, an electron beam focusing coil assembly 5 and an electron beam deflecting coil assembly 6.

The electrons passed through the thin film I have sufficient energy and impinge against gas particles in the atmosphere to cause ionization of the gas particles. The ionized gas particles are charged to emit one or more electrons. The electron or electrons emitted from the ionized gas particles are accelerated by an electric field, if there is such an electric field, to ionize the gas particles successively and cumulatively. The interaction between the electrons and the gas particles as described above is repeated to multiply substantially the number of electrons.

Referring to FIG. 2 showing the basic principle of the present invention, a partition 7 in the fonn of a thin film of conductive nature isolates one atmosphere A: from another atmosphere A,. A DC power supply 10 is connected between the partition 7 and an electrode 8 so that an electric field is established in the space defined between the partition 7 and the electrode 8. Electrons accumulate on a film 9 of electrical insulator and charges carried by the accumulated electrons produce an electrostatic pattern.

The above phenomenon will be more quantitatively discussed with reference to FIG. 4, in which a is the so-called first Townsend's coefiicient. FIG. 4 shows the relation between the gas pressure P, the strength of an electric field E and the first Townsend's coefficient a which represents the number of electrons which are produced by ionization as one electron moves a distance of 1 cm.

FIG. 5 is a graphic representation of Paschens law which discloses the condition under which discharge is started in various gases. While FIG. 4 teaches that amplification becomes higher as the strength of electric field becomes stronger, the electric field becomes stronger, the strength of electric field can not exceed the condition set forth in FIG. 5.

For example, suppose that the distance between the thin film 7 and the electrode 8 is l00p.m. and the voltage thereacross is 1,000 volts, then 01 760 is derived from FIG. 4. Therefore, the electrons ionized on the surface of the thin film 7 on the side of the atmosphere A, are multiplied by exp. (760 X 1/100) 2,000 times when they reach the thin insulator film 9 which is a recording medium. This is the maximum value and actually the above value is smaller than the maximum. The divergence of the electrons subjected to the above amplification is in the order of several ten pm.

In FIG. 3 there is shown one fonn of the device of the present invention utilizing the electron-multiplying action described above. The device comprises a recording cathoderay tube 15 having an electron-beam transmissive thin film l I. An electrode 8' for producing an electric field may be coated or otherwise associated with the back face of an electrostatic recording sheet 9 being an electrical insulator. In this device, an electron beam of a small quantity and having a small diameter suffices to effect an increase in the resolution since the sensitivity is quite high.

In FIG. 6, there is shown another embodiment of the present invention. The device comprises a recording cathode,- ray tube equipped with an electron-beam penetrative thin film 12 utilizing the above-described principle. The electron-beam penetrative thin film 12 is backed up by a supporting member and is reinforced by a member 13 which acts both as a reinforcement for the film 12 and as a means for preventing any deterioration of the resolution. An electrode 8' disposed on the back face of an electrostatic recording sheet 9' is electrically connected with the thin film 12 through a DC power supply 10.

FIG. 7 is an enlarged detailed view of the portion in the vicinity of the electron-beam transmissive window in FIG. 6. A charge image formed on the recording sheet 9 can be converted into a visible image by means of development with a toner or, when a thermoplastic resin is used, by the Schlieren method. Since the number of electrons can thus be multiplied within a gaseous atmosphere having an electric field established therein, an electron beam of a small quantity, hence a very small spot size suffices, thereby remarkably improving the sensitivity and resolution of the recorded image.

A novel recording device can be obtained by employing a recording tube of the kind described above as a means for forming an electrostatic charge image. An embodiment of the present invention employing such a recording tube will be described with reference to FIG. 8. The recording device comprises a recording cathode-ray tube 16 of the kind described above. A cylindrical member or drum 17 of electrical insulator is disposed opposite to the cathode-ray tube 16 to receive an electron beam therefrom, and is internally provided with an electrode 18 for establishing an electric field between it and the cathode-ray tube 16 through the insulator drum 17. A toner supplier 19 is disposed above the insulator drum 17 to supply a toner onto the drum 17 depending on the charge carried by the drum 17. A recording sheet 20 is in contact with the insulator drum 17. An electrode 21 applies an electric charge to the recording sheet 20 by corona discharge. An electrode 22 is disposed behind the recording sheet 20 so as to produce an electric field between it and the electrode 18. One of the electrodes 21 and 22 can be eliminated because their performances are substantially the same. A heater 23 is also disposed behind the recording sheet 20 so as to thermally fix the toner to the recording sheet 20. A brush 24 is associated with the insulator drum 17 to mechanically clean the surface of the drum 17 after the toner on the drum 17 has been trans ferred to the recording sheet 20. A heater 25, a light source 26 and a corona discharge electrode 27 are further associated with the drum 17 for uniformalizing or erasing the electric charge on the drum 17 after cleaning. In this case some parts can also by eliminated.

Although the idea of supplying an electric charge on an electrical insulator depending on a signal and transferring a toner to a recording sheet depending on the charge image formed on the insulator is already known in the art, the recording device according to the present invention is far more useful than prior art devices in that it employs means including an insulator drum and an electron-beam transmissive window for supplying the electrons passed through the window to the insulator drum. Another advantage resides in the fact that the electrons can easily penetrate the insulator drum because the electrons supplied to the insulator have an energy of the order of several ten Kev. The present invention is further advantageous in that the undesirable emission of secondary electrons can be prevented by the application of a voltage to the electrode 18 relative to the thin film and in that the electron-multiplying action can be effected as described previously. It will be understood that the device according to the present invention differs conspicuously from prior art devices in the features pointed out hereabove.

As the insulator drum 17 rotates in a direction of the arrow, the charge image formed on the surface of and partly within the insulator drum 17 comes to a position beneath the toner supplier 19. Generally, the toner is a mixture of a powdery plastic resinous ,material and carbon powder. The toner dispensed on the insulator drum 17 attaches to the insulator drum 17 depending on the charge image carried by the drum 17. The tower itself may be charged to enhance the effect of,

attachment. In lieu of the powdery toner, liquid ink which is a mixture of an insulator solution and a powdery coloring agent such as as carbon powder may be sprayed onto the charge image carried by the insulator drum 17 to attach the ink depending on the charge image on the insulator drum 17. As the insulator drum rotates further, the toner irnage formed on the insulator drum 17 comes to a position at which it contacts the recording sheet 20. The recording sheet 20 may be a part of a roll of paper or a rectangular strip or may be severed off from a roll of paper immediately before it engages the insulator drum 17. The toner image on the insulator drum I7 is transferred onto the recording sheet 20 at the position at which both contact each other. There are various methods of transfer printing. For example, the toner image may be attracted to the recording sheet 20 by the action of the electrode 21. In this case, the charge applied by the corona discharge must be held on the recording sheet 20 while the toner image is being attracted from the insulator drum 17. In another case, voltage may be applied to the electrode 22 for the transfer printing of the toner image from the insulator drum 17 to the recording sheet 20.

The image on the insulator drum 17, which may be formed either by the liquid ink or by the toner, can be transfer-printed on the recording sheet 20 by application of pressure thereto. As the recording sheet 20 moves toward the heater 23, the plastic material in the toner is heated to melt so that the toner can firmly be bonded to the recording sheet 20. As the insulator drum 17 rotates further, any toner that is remaining is cleared from the insulator drum 17 by means of the brush 24, heater 25, light source 26 and discharge electrode 27 so that any irregularity of the remaining charge can be eliminated or such charge can be erased.

In another embodiment of the present invention shown in FIG. 9, the device comprises a cathode-ray tube 16 of the kind described above, a thin endless tape 17 of electrical insulator, an electrode 18', a toner supplier 19, a corona discharge electrode 21, an electrode 22 and a heater 23. The elements 18', 19, 21, 22 and 23 are disposed within the space defined by the endless film 17. In this embodiment, a toner image may be formed on that surface of the insulator tape 17 which is opposite to the surface of which a charge image is formed by electrons emitted from the cathode-ray tube 16. An electrode 28 is disposed opposite to the electrode 22 in order to establish an electric field therebetween.

A plurality of such devices or processes may be arranged in series to obtain a multicolored record. It will be appreciated that the device according to the present invention finds its useful applications in facsimile receivers. output units of electronic computers, electrophotographic processors linotypes and others since the size, energy, position and quantity of the electron beam can be controlled at very high speeds.

What is claimed is:

l. A recording device comprising means for directing a recording information-bearing electron beam through an electron-permeable thin film from a first atmosphere to a second atmosphere, a recording medium sensitive to incident charged particles, and means for establishing an electric field for ionization of a gas substance of said second atmosphere and multiplication thereof responsive to the incident electron beam from said film between said film and said recording medium in order to fonn the corresponding electrostatic image on the recording medium.

2. An electrostatic recording device comprising a cathoderay tube having a thin film window opposite its electron gun; electrode means disposed in spaced relationship with said thin film; an electrostatic recording sheet spaced from said thin film and positioned adjacent the face of said electrode means towards the thin film; and DC supply means connected between said thin film and said electrode means to supply a positive voltage to said electrode means; and means to form an electrostatic charge on said recording sheet, including means to multiply the number of electrons by ionization of a gas between saidv thin film and said recording sheet dependent upon the number of incident electrons passing through said thin film for deposition on said recording sheet.

3. A recording device as claimed in claim 2 wherein said thin film comprises a metal oxide.

4. A recording device as claimed in claim 3 wherein said thin film comprises a semiconductor oxide.

5. A recording device as claimed in claim 2 having means for applying a developing material to the charge image to obtain a developed image, and means for transfer-printing the developed image to a recording sheet.

6. A recording device as claimed in claim 5 in which the recording sheet has the form of rotatable drum means for carrying the outer surface thereof successively past a window in said thin film, the means for applying the developing material and the transfer-printing means.

7. A recording device as claimed in claim 5 wherein said transfer-printing means comprises electrode means for attracting the toner image to a record member from the recording sheet.

8. A recording device as claimed in claim 5, having means to carry the inner surface of said recording sheet in the form of a thin endless tape successively past a window in said thin film, the means for applying the developing material and the transfer-printing means.

9. A recording device as claimed in claim 8, wherein said recording sheet has temperature-dependent semiconductive properties, said device further comprising heater means for rendering said sheet conductive to dissipate any residual electric charge after the transfer-printing.

10. A recording device as claimed in claim 8, wherein said recording sheet is photoconductive, said device further comprising light source means for rendering said sheet conductive to dissipate any residual electric charge after the transferprinting.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,611,418 Dated October 5, 1971 Inventor) Yoshihiro UNO et al It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

In the Claim for Convention Priority, two of the four Japanese applications should read Signed and soalod this 18th day of April 1972.

( s EAL fittest:

IEDWLRD MFLETCIIER, JR. H T'ISCHALK Attescing Officer Commissioner of Patents 42/65873 and 42/66759- instead of 4/65873 and 44/66759".

:ORM P0405) (10-69) uscoMM-oc uoavs-F-ao 9 U 5 GDVERNHENT PRlNTING OFFICE: 1919 0-355!!! 

2. An electrostatic recording device comprising a cathode-ray tube having a thin film window opposite its electron gun; electrode means disposed in spaced relationship with said thin film; an electrostatic recording sheet spaced from said thin film and positioned adjacent the face of said electrode means towards the thin film; and DC supply means connected between said thin film and said electrode means to supply a positive voltage to said electrode means; and means to form an electrostatic charge on said recording sheet, including means to multiply the number of electrons by ionization of a gas between said thin film and said recording sheet dependent upon the number of incident electrons passing through said thin film for deposition on said recording sheet.
 3. A recording device as claimed in claim 2 wherein said thin film comprises a metal oxide.
 4. A recording device as claimed in claim 3 wherein said thin film comprises a semiconductor oxide.
 5. A recording device as claimed in claim 2 having means for applying a developing material to the charge image to obtain a developed image, and means for transfer-printing the developed image to a recording sheet.
 6. A recording device as claimed in claim 5 in which the recording sheet has the form of rotatable drum means for carrying the outer surface thereof successively past a window in said thin film, the means for applying the developing material and the transfer-printing means.
 7. A recording device as claimed in claim 5 wherein said transfer-printing means comprises electrode means for attracting the toner image to a record member from the recording sheet.
 8. A recording device as claimed in claim 5, having means to carry the inner surface of said recording sheet in the form of a thin endless tape successively past a window in said thin film, the means for applying the developing material and the transfer-printing means.
 9. A recording device as claimed in claim 8, wherein said recording sheet has temperature-dependent semiconductive properties, said device further comprising heater means for rendering said sheet conductive to dissipate any residual electric charge after the transfer-printing.
 10. A recording device as claimed in claim 8, wherein said recording sheet is photoconductive, said device further comprIsing light source means for rendering said sheet conductive to dissipate any residual electric charge after the transfer-printing. 